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题名: Elucidation of the reaction mechanisms and diastereoselectivities of phosphine-catalyzed [4+2] annulations between allenoates and ketones or aldimines
作者: Qiao, Yan1;  Han, Ke-Li1
刊名: ORGANIC & BIOMOLECULAR CHEMISTRY
发表日期: 2012
DOI: 10.1039/c2ob25965f
卷: 10, 期:38, 页:7689-7706
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Physical Sciences
类目[WOS]: Chemistry, Organic
研究领域[WOS]: Chemistry
英文摘要: The phosphine-catalyzed [4 + 2] annulations between allenoates and electron-poor trifluoromethyl ketones or N-tosylbenzaldimine dipolarophiles have been investigated in continuum solvation using density functional theory (DFT) calculations. The detailed reaction mechanisms as well as the high cis-diastereoselectivities of the reactions have been firstly clarified. Our calculated results reveal that the whole catalytic process is presumably initiated with the nucleophilic attack of phosphine catalyst at the allenoate to produce the zwitterionic intermediate M1, which subsequently undergoes gamma-addition to the electron-poor C=O (or C=N) dipolarophile to form another intermediate M2. The following [1,3] hydrogen shift of M2 is demonstrated to proceed via two consecutive proton transfer steps without the assistance of protic solvent: the anionic O6 (or N6) of M2 first acts as a base catalyst to abstract a proton from C1 to produce the intermediate M3, and then the OH (or NH) group can donate the acidic proton to C3 to complete the [1,3] hydrogen shift and generate the intermediate M4. Finally, the intramolecular Michael-type addition followed by the elimination of catalyst furnishes the final product. High cis-diastereoselectivities are also predicted for both the two reactions, which is in good agreement with the experimental observations. For the reaction of allenoates with trifluoromethyl ketones, the first proton transfer is found to be the diastereoselectivity-determining step. The cumulative effects of the steric repulsion, electrostatic interaction as well as other weak interactions appear to contribute to the relative energies of transition states leading to the diastereomeric products. On the contrary, in the case of N-tosylbenzaldimines, the Michael-type addition is found to be the diastereoselectivity-determining step. Similarly, steric repulsion, as well as electrostatic interaction is also identified to be the dominant factors in controlling the high cis-diastereoselectivity of this reaction.
关键词[WOS]: HIGHLY FUNCTIONALIZED TETRAHYDROPYRIDINES ;  BAEYER-VILLIGER REARRANGEMENT ;  3+2 CYCLOADDITION REACTIONS ;  DIELS-ALDER REACTIONS ;  DENSITY FUNCTIONALS ;  THERMOCHEMICAL KINETICS ;  NONCOVALENT INTERACTIONS ;  ORGANIC-SYNTHESIS ;  BENCHMARK SUITES ;  CHEMISTRY
语种: 英语
WOS记录号: WOS:000308660300008
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/143127
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Mol React Dynam, Dalian 116023, Peoples R China

Recommended Citation:
Qiao, Yan,Han, Ke-Li. Elucidation of the reaction mechanisms and diastereoselectivities of phosphine-catalyzed [4+2] annulations between allenoates and ketones or aldimines[J]. ORGANIC & BIOMOLECULAR CHEMISTRY,2012,10(38):7689-7706.
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